Why are you at a loss? The cap says use 5W-30 and you can buy 5W-30 in Castrol High Mileage at Walmart. So, what’s the problem use 5W-30. If you live in Florida, Arizona or some other warm weather year round state and want to use 10W-30 no big deal. If you live in cold climates the 5W-30 will make it easier on your starting motor, will circulate and lubricate better as the car warms up, and you’ll get more mpg.
Whatever you do, it won’t make a lot of difference. So, why not use 5W-30 as the cap states.